1. Field of the Invention
The present invention relates to a method of tying a knot in chain-stitching, which is formed at the end of the chain-stitching and which cannot easily be untied, and also relates to a chain-stitch sewing machine for forming such a knot.
2. Discussion of the Related Art
Referring to FIG. 26 which shows a conventional knot in a yarn, which is formed by a single chain-stitch-type button sewing machine, the type of this knot corresponds to Class Symbols 101 and 107 which are specified in JIS (Japanese Industrial Standard)-L-0120.
As shown in FIG. 26, a button 203 is sewn onto a cloth by a single chain-stitch with the use of a yarn 201. At the final stage of sewing the button, a second loop 205, which is formed during formation of a stitch and which is one stitch ahead of the final stitch, is passed through a first loop 204 that is formed during formation of a stitch which is two stitches ahead of the final stitch, and the leading end part 206 of the yarn is passed under the second loop 205. This leading end part 206 cuts a third loop (not shown) formed during the formation of a final stitch by cutting the third loop with a cutting blade.
In this situation, the knot is never being loosened even though pulling the leading end part 206 of the yarn is being pulled in the direction of the arrow A.
However, with the above-mentioned knot of the chain-stitch, if the leading end part of the yarn 206 comes off from the second loop 205, as shown in FIG. 27, the second loop 205 is likely to come off from the first loop 206 when the leading end part 206 is pulled in the direction of the arrow B, as shown in FIG. 28, and further, all loops are loosened, when the leading end part is further pulled, so that the button 203 is separated from the cloth 202.